NASA is in the process of building the Orion space capsule and must nondestructively inspect the heat shield prior to launch; however, the materials that must survive the rigors of reentry also prove difficult to inspect. Electromagnetic techniques like X-ray and terahertz can be used to detect three-dimensional defects like voids, but two-dimensional defects, like the kissing unbond, are undetectable by the same techniques. In a previous paper, the authors describe a customized pulse-echo ultrasonic inspection technique capable of detecting voids and the elusive kissing unbonds in a laboratory environment. The technique is described in detail regarding the best couplant to use, transducer and frequency selection, and signal processing techniques. In the current paper, the technique is significantly expanded to be used on the actual heat shield. It describes the best protective interface to use between the heat shield and the transducer, the scanning system, and the image processing techniques used to form C-scans. Additionally, results are discussed that demonstrate the technique’s ability to size discontinuities.
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